Water cleaning system, water cleaning method, startup method for water cleaning system, and water cleaning unit

ABSTRACT

A water cleaning system  1  includes an aerobic region  90  including breeding water  9  containing organic matter and oxygen, an aerobic layer  6  linking with the aerobic region  90  and inhabited by aerobic bacteria, a facultative anaerobic layer  5  provided adjacent to the aerobic layer  6  and inhabited by facultative anaerobic bacteria, an obligatory anaerobic layer  4  provided adjacent to the facultative anaerobic layer  5 , inhabited by obligatory anaerobic bacteria, and made of andosol  40 , an anaerobic space  3  having an anaerobic environment, allowing the obligatory anaerobic bacteria inhabiting the obligatory anaerobic layer  4  and products therefrom to flow therein, and a tube  18  as linking means linking the anaerobic space  3  and the aerobic region  90.

TECHNICAL FIELD

The present invention relates to a water cleaning system, a watercleaning method, a startup method for the water cleaning system, and awater cleaning unit, which require neither a separate device forsupplementing a filtering function nor processes of replacing water andsand semipermanently or for a long period of time.

BACKGROUND ART

When hydrosphere organisms are bred in a retention tank such as a watertank, organic matter derived from excrement thereof and the likegenerates toxic ammonia, nitric acid, and the like. Accordingly, theexcrement and the like have been conventionally removed by using afiltration device as well as periodically performing a water replacementprocess of replacing breeding water in the retention tank with freshwater and a replacement process of replacing sand in the retention tankwith new sand. However, an external filtration device of a type providedabove the retention tank or the like requires high costs forinstallation and maintenance management. These costs will increase ifthe retention tank is large in scale. Furthermore, the processes ofreplacing water and sand require time and effort and may damagehydrosphere organisms more than a little.

A breeding system not including such an external filtration devicementioned above is typically exemplified by a breeding system ofJaubert's Monaco System disclosed in Patent Document 1. This breedingsystem includes a water permeable plate member providing a raisedbottom, a sand layer provided on the plate member, an aerobic layerprovided on the sand layer, having an aerobic environment, and receivinglight, and a facultative anaerobic layer provided under the sand layer,having an anaerobic environment, and receiving no light. Aerobicbacteria inhabit the aerobic layer whereas facultative anaerobicbacteria inhabit the facultative anaerobic layer. The aerobic bacteriaand the facultative anaerobic bacteria decompose toxic ammonia, nitrousacid, nitric acid, and the like generated from organic matter to exert afiltering function. The breeding system of Jaubert's Monaco Systemtypically does not require the external filtration device mentionedabove.

CITATION LIST Patent Document

-   PTD 1: Japanese Patent Laying-Open No. 2002-223664

SUMMARY OF INVENTION Technical Problem

In the above breeding system of Jaubert's Monaco System, however, deadbodies of aerobic bacteria and facultative anaerobic bacteria as well assubstances generated by these bacteria accumulate below the plate memberor at the bottom of the retention tank. These substances include sulfurcompounds containing toxic sulfate ions. If a large amount of thesubstances accumulate, the substances may pass through the aerobic layerand the facultative anaerobic layer and rush upward to kill hydrosphereorganisms. The breeding system of Jaubert's Monaco System thus has aninsufficient filtering function and fails to detoxify toxic substancesgenerated from excrement of hydrosphere organisms and the like. It isthus necessary to separately provide a device for supplementing thefiltering function or perform the processes of replacing water and sandin order to sufficiently inhibit contamination of breeding water. Thebreeding system of Jaubert's Monaco System allows a limited number ofhydrosphere organisms to be bred therein, and may fail to exertsufficient cleaning ability due to increase in amount of excrement andthe like as hydrosphere organisms grow even in a case where the numberof hydrosphere organisms is less than or equal to the breedable number,in which case the number of hydrosphere organisms may have to be reducedhalfway. Continuous breeding with insufficient cleaning ability willlead to death of all hydrosphere organisms in the retention tank. Asdescribed above, notable development in processing excrement and thelike has not been made to tools and devices for cleaning water for manyyears. Such a situation is a great burden to breeders (managers).

Such sulfur compounds are possibly generated in a water tank as well asin a hydrosphere organisms farm provided in the sea or the like due todecomposition of organic matter in water by inhabiting bacteria.Hydrosphere organisms will be damaged if a large amount of sulfurcompounds are generated.

The present invention has been made to effectively solve these problems,and an object thereof is to provide a water cleaning system, a watercleaning method, and a startup method for the water cleaning system,which can inhibit accumulation of toxic substances derived fromexcrement of hydrosphere organisms and the like as well as can requireneither a separate device for supplementing a filtering function norprocesses of replacing water and sand semipermanently or for a longperiod of time.

Another object of the present invention is to provide a water cleaningunit that can facilitate the water cleaning system and the watercleaning method in a hydrosphere organisms farm provided in a retentiontank such as a water tank, in the sea, or the like.

Solution to Problem

The present invention provides the following means in order to achievethese objects.

A water cleaning system according to the present invention includes: anaerobic region including organic matter and oxygen; an aerobic layerlinking with the aerobic region and inhabited by aerobic bacteria; afacultative anaerobic layer provided adjacent to the aerobic layer andinhabited by facultative anaerobic bacteria; an obligatory anaerobiclayer provided adjacent to the facultative anaerobic layer, inhabited byobligatory anaerobic bacteria, and made of a soil material; an anaerobicspace having an anaerobic environment, allowing the obligatory anaerobicbacteria inhabiting the obligatory anaerobic layer and productstherefrom to flow therein; and linking means linking the anaerobic spaceand the aerobic region.

The soil material has only to have a property, a function, and the likesimilar to those of naturally existing soil, such as leaf mold. The soilmaterial is not limited to the naturally existing soil but can beproduced artificially. The soil material having a property, a function,and the like similar to those of soil allows inhabitation of obligatoryanaerobic bacteria similarly to soil. Furthermore, when the soilmaterial forms a layer, organic matter, microorganisms, and the like aremovable in the layer and an anaerobic environment can be provided in thelayer. The soil material is not particularly limited in shape thereofinsofar as the soil material achieves the property, the function, andthe like. The soil material can be formed into a layer by pressing, forexample, soil and other particulate substances, or can have a massiveshape like sponge, so as to configure a layer by itself. A state wherethe aerobic region and the aerobic layer link with each other indicatesa state where organic matter, oxygen, water, and the like, if any in theaerobic region, are movable to the aerobic layer. A state where theanaerobic space and the aerobic region link with each other indicates astate where obligatory anaerobic bacteria, hydrogen sulfide, water, andthe like, if any in the anaerobic space, are movable to the aerobicregion.

In such a configuration, organic matter in the aerobic region reachesthe aerobic layer and subsequently reaches the facultative anaerobiclayer, and is decomposed by aerobic bacteria and facultative anaerobicbacteria inhabiting the aerobic layer and the facultative anaerobiclayer, respectively. Decomposed matter thus obtained then reaches theobligatory anaerobic layer and is decomposed by obligatory anaerobicbacteria. Sulfur compounds are decomposed into hydrogen sulfide bysulfate-reducing bacteria that are obligatory anaerobic bacteria and areinhabitable only under an anaerobic condition. Hydrogen sulfide thusgenerated is reduced in toxicity in at least one of the aerobic region,the aerobic layer, the facultative anaerobic layer, the obligatoryanaerobic layer, and the anaerobic space. Reduction in toxicity meansreducing toxicity to hydrosphere organisms. Specifically, hydrogensulfide is reduced in toxicity by reacting with an iron component inwater while moving, along with sulfate-reducing bacteria, to the aerobicregion through the linking means into iron sulfide less toxic tohydrosphere organisms than hydrogen sulfide, or by being converted todifferent sulfur compounds less toxic to hydrosphere organisms thanhydrogen sulfide by sulfur oxidizing bacteria, photosynthetic bacteria,and the like inhabiting the aerobic layer and the like. Thesulfate-reducing bacteria having moved to the aerobic region can inhabiteven an aerobic environment by reacting with iron sulfide. Thesulfate-reducing bacteria reach a surface of the aerobic layer anddecompose organic matter if the organic matter therein is relativelylarge in amount but come into a dormant state if the organic mattertherein is relatively small in amount so as to increase in amount oforganic matter to be decomposed. Decomposition of organic matter inwater as well as reduction in toxicity of hydrogen sulfide generatedthrough the decomposition as described above can inhibit accumulation oftoxic matter derived from the organic matter neither with a separatedevice for supplementing a filtering function nor with processes ofreplacing water and sand semipermanently or for a long period of time,and can clean water in the retention tank such as a water tank or waterin a hydrosphere organisms farm provided in the sea or the like. In acase where the water cleaning system according to the present inventionis applied to breeding of hydrosphere organisms, there is no need toreduce the number of bred hydrosphere organisms even after hydrosphereorganisms have grown but the number of breedable hydrosphere organismscan be increased in comparison to a conventional case.

In order to facilitate formation of the anaerobic space and stably keepthe anaerobic space for a long period of time, preferably, an opening ata top of a hollow member is closed by a meshed member having waterpermeability and blocking passage of the soil material, the soilmaterial surrounds the hollow member and the meshed member to form theanaerobic space in the hollow member.

In order to multiply obligatory anaerobic bacteria easily and reliablyas well as form the obligatory anaerobic layer that can decompose asufficient amount of organic matter, the soil material is preferablyandosol.

In order to keep water containing organic matter slightly alkaline likeseawater to keep an environment appropriate for breeding saltwaterfishes and inhibit reduction in activity of sulfate-reducing bacteria,the aerobic layer is preferably provided, on a surface thereof, with alayer made of coral sand.

According to another method of easily forming the anaerobic space,preferably, the retention tank includes a nontransmissive portionblocking transmission of light from a lower portion in a side surfaceand from a bottom surface, a meshed member having water permeability andblocking passage of the soil material is entirely provided at a lowerportion in the retention tank so as to be apart from an inner bottomsurface of the retention tank, the meshed member has an upper surfacecovered with the soil material and the anaerobic space is formed betweenthe meshed member and the inner bottom surface.

A water cleaning method according to the present invention includes:installing, in water, a first bacteria inhabitable portion made of asoil material that is inhabitable by obligatory anaerobic bacteria andpreliminarily pressed into a massive shape, forming, in water, a secondbacteria inhabitable portion that is adjacent to the first bacteriainhabitable portion, has a particulate carrier, and is inhabitable byfacultative anaerobic bacteria, a third bacteria inhabitable portionthat is adjacent to the second bacteria inhabitable portion, has aparticulate carrier, and is inhabitable by aerobic bacteria, and ananaerobic space that has an anaerobic environment and links with thefirst bacteria inhabitable portion, locating, at a position linking withthe third bacteria inhabitable portion, an aerobic region includingorganic matter and oxygen, and linking the aerobic region and theanaerobic space, and forming an obligatory anaerobic layer bymultiplying obligatory anaerobic bacteria in the first bacteriainhabitable portion, forming a facultative anaerobic layer bymultiplying facultative anaerobic bacteria in the second bacteriainhabitable portion, forming an aerobic layer by multiplying aerobicbacteria in the third bacteria inhabitable portion, causing thesebacteria to decompose the organic matter in the aerobic region, andmoving the obligatory anaerobic bacteria flowing out of the obligatoryanaerobic layer and products therefrom from the anaerobic space to theaerobic region.

A state where the first bacteria inhabitable portion and the anaerobicspace link with each other indicates a state where obligatory anaerobicbacteria, products therefrom, water, and the like, if any in the firstbacteria inhabitable portion, are movable to the anaerobic space. Astate where the aerobic space and the third bacteria inhabitable portionlink with each other indicates a state where organic matter, oxygen,water, and the like, if any in the aerobic space, are movable to thethird bacteria inhabitable portion. A state where the anaerobic spaceand the aerobic region link with each other indicates a state whereobligatory anaerobic bacteria, hydrogen sulfide, water, and the like, ifany in the anaerobic space, are movable to the aerobic region.

In accordance with such a method, the aerobic region including organicmatter is located at a position linking with the third bacteriainhabitable portion and the aerobic region and the anaerobic space arebrought into the linking state. Accordingly, obligatory anaerobicbacteria multiply in the first bacteria inhabitable portion to form theobligatory anaerobic layer, facultative anaerobic bacteria multiply inthe second bacteria inhabitable portion to form the facultativeanaerobic layer, and aerobic bacteria multiply in the third bacteriainhabitable portion to form the aerobic layer. Similarly to the watercleaning system according to the present invention, decomposition oforganic matter in water as well as reduction in toxicity of hydrogensulfide generated through the decomposition can thus inhibitaccumulation of toxic matter derived from the organic matter neitherwith a separate device for supplementing a filtering function nor withprocesses of replacing water and sand semipermanently or for a longperiod of time. In a case where the water cleaning method according tothe present invention is applied to breeding of hydrosphere organisms,there is no need to reduce the number of bred hydrosphere organisms evenafter hydrosphere organisms have grown but the number of breedablehydrosphere organisms can be increased in comparison to a conventionalcase. Furthermore, provision of the first bacteria inhabitable portionpreliminarily pressed into a massive shape enables artificial formationof a decomposition cycle of organic matter for causing the reduction intoxicity of hydrogen sulfide at a desired position in a short period oftime.

In order to start up the water cleaning system, it is preferred to,using a cylindrical member as the linking means, apply light to theaerobic layer in a state where the aerobic region includes organicmatter, and simultaneously supply gas from gas supply means into thecylindrical member to generate a stream from the anaerobic space towardabove the aerobic layer in the cylindrical member, and keep the statefor a predetermined period of time.

A water cleaning unit according to the present invention is used toconstruct the water cleaning system. An exemplary water cleaning unitincludes: a bacteria inhabitable portion in a massive shape, made of asoil material and inhabitable by obligatory anaerobic bacteria; and acylindrical member that has a first open portion and a second openportion, has a length to extend from a first end to a second end of thebacteria inhabitable portion, wherein the second open portion ispositioned apart from the bacteria inhabitable portion by apredetermined distance at the second end of the bacteria inhabitableportion when the first open portion is positioned to face the first endof the bacteria inhabitable portion.

In such a configuration, the water cleaning unit is immersed in watercontaining organic matter and the particulate carrier or the like issupplied to form the aerobic layer and the facultative anaerobic layeron a surface provided with a second end of the cylindrical member in thebacteria inhabitable portion, so that the bacteria inhabitable portioncan be provided, at the first end thereof, with a closed space usingclosed space forming means or the like. The second open portion ispositioned apart from the bacteria inhabitable portion by thepredetermined distance when the cylindrical member is positioned to facethe first open portion at the first end of the bacteria inhabitableportion. The anaerobic space linking with the aerobic region, theaerobic layer, the facultative anaerobic layer, the obligatory anaerobiclayer, and the aerobic region can be easily formed with the second endof the cylindrical member not closed by the particulate carrier or thelike. The bacteria inhabitable portion is formed into a massive shape bypreliminarily pressing the soil material, so as to easily form theobligatory anaerobic layer in water as well as shorten a startup periodof time necessary for establishing the decomposition cycle of organicmatter.

In order to form the anaerobic space more easily, preferably, the watercleaning unit further includes: a closed space surrounded with closingmeans that is at least partially formed by the bacteria inhabitableportion; wherein the cylindrical member has a length to extend from theclosed space through the closing means, and the second open portion ispositioned apart from the bacteria inhabitable portion by apredetermined distance when the first open portion is positioned to facethe closed space.

In order to inhibit the bacteria inhabitable portion from crumbling dueto loosening of the soil material and inhibit the soil material fromflowing out of the water cleaning unit immersed in water, preferably, atleast a surface, not provided with the cylindrical member projectingtherefrom, of the bacteria inhabitable portion is covered with asurrounding member blocking passage of the soil material.

In order to prevent light from entering the closed space without use ofany other member upon configuring the water cleaning system including anordinary transparent water tank, the surrounding member preferably has alight shielding property.

In order to inhibit the soil material from entering the closed space,the bacteria inhabitable portion and the closed space are preferablyprovided therebetween with a meshed member having water permeability andblocking passage of the soil material.

For construction of the water cleaning system including the watercleaning unit described above, the particulate carrier occasionallyneeds to be supplied to form the facultative anaerobic layer and theaerobic layer. In order to provide the water cleaning unit that does notrequire time and effort therefor, preferably, the water cleaning unitfurther includes a particulate carrier inhabitable by aerobic bacteriaand facultative anaerobic bacteria to form, when the bacteriainhabitable portion inhabitable by obligatory anaerobic bacteria isdefined as a first bacteria inhabitable portion, a second bacteriainhabitable portion that is adjacent to the first bacteria inhabitableportion and is inhabitable by facultative anaerobic bacteria and a thirdbacteria inhabitable portion that is adjacent to the second bacteriainhabitable portion and is inhabitable by aerobic bacteria.

In order to achieve reduction in weight of the water cleaning unit, thebacteria inhabitable portion is preferably dry.

In order to achieve use of a plurality of stacked water cleaning unitsor facilitate installation also at an uneven place such as the bottom ofthe sea, preferably, the water cleaning unit further includes a supportleg for securing a predetermined gap from an installation surface.

Advantageous Effects of Invention

The present invention described above can provide a water cleaningsystem, a water cleaning method, a startup method for the water cleaningsystem, and a water cleaning unit, which inhibit accumulation of toxicmatter derived from organic matter and reduce toxicity of hydrogensulfide generated from organic matter due to action of bacteria byconverting into a less toxic substance or the like, so as to be usefulneither with a device for supplementing a filtering function nor withprocesses of replacing water and sand semipermanently or for a longperiod of time.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view of a water cleaning unit according to a firstembodiment of the present invention.

FIG. 2 is a sectional view of a state where a cylindrical member and thelike are attached to the cleaning unit.

FIG. 3 is a sectional view of a state where a second bacteriainhabitable portion and a third bacteria inhabitable portion are furtherattached to the cleaning unit.

FIG. 4 is a sectional view of a water cleaning system according to thefirst embodiment provided with the cleaning unit.

FIG. 5 is a pattern view of circulation of organic matter in thecleaning system.

FIG. 6 is an explanatory flowchart of a startup method for the cleaningsystem.

FIG. 7 is a sectional view of a state where a support leg is furtherattached to the cleaning unit.

FIG. 8 is a sectional view of a water cleaning unit according to asecond embodiment of the present invention.

FIG. 9 is a sectional view of a state where a cylindrical member and thelike are attached to the cleaning unit.

FIG. 10 is a sectional view of a water cleaning system according to thesecond embodiment provided with the cleaning unit.

FIG. 11 is a sectional view of a water cleaning unit according to athird embodiment of the present invention.

FIG. 12 is a sectional view of a water cleaning unit according to amodification example of the first embodiment.

DESCRIPTION OF EMBODIMENTS First Embodiment

The first embodiment according to the present invention will now bedescribed below with reference to FIGS. 1 to 7.

As depicted in FIG. 1, a water cleaning unit 100 according to the firstembodiment of the present invention is used as a breeding unit forhydrosphere organisms, and includes a bacteria inhabitable portion 140having a massive shape and inhabitable by obligatory anaerobic bacteria.Bacteria inhabitable portion 140 is provided with a cylindrical memberinsertion hole 40 a serving as a penetrating portion penetrating from afirst end to a second end of bacteria inhabitable portion 140.

Bacteria inhabitable portion 140 is dry and is formed by pressingandosol 40 serving as a soil material having an aggregate structure intoa substantially rectangular shape in a plan view. Such a dry stateincludes a state of containing no moisture as well as a state ofcontaining some moisture. Bacteria inhabitable portion 140 has a recessprovided therein with a hollow member 30 having an opening 30 b depictedin FIG. 2. Cylindrical member insertion hole 40 a is provided thereinwith a tube 18. Furthermore, bacteria inhabitable portion 140 has itsperiphery surrounded with a surrounding member 131. There is thusprovided a closed space 130 at least partially surrounded with bacteriainhabitable portion 140, with tube 18 extending from closed space 130.Hollow member 30 surrounds both ends (lateral portions) in a firstdirection X (the horizontal direction in the present embodiment) ofclosed space 130. Surrounding member 131 surrounds a first end (thebottom in the present embodiment) in a second direction Y (the verticaldirection in the present embodiment), which is perpendicular to firstdirection X, of closed space 130 Furthermore, bacteria inhabitableportion 140 surrounds a second end (the top in the present embodiment)in second direction Y of closed space 130. Hollow member 30 has acylindrical shape with both ends in second direction Y being open. Thereare provided two hollow members 30 so as to be apart from each other.Hollow members 30 each have an upper opening 30 a mounted with alatticed or slotted plate member 31 having a surface covered with ameshed member 32. The periphery except for a first end in seconddirection Y of hollow member 30 is covered with andosol 40 configuringbacteria inhabitable portion 140. Meshed member 32 blocks passage ofandosol 40 and has water permeability, so as to inhibit andosol 40 inbacteria inhabitable portion 140 from entering closed space 130 fromabove. Meshed member 32 can be exemplified by a meshed cloth, a fibroussheet, or the like having such functions. Surrounding member 131 has alight shielding property and a sheet or plate shape to block passage ofandosol 40 and oxygen. As depicted in FIG. 2, surrounding member 131covers both surfaces 140 b in first direction X, a first surface 140 cin second direction Y of bacteria inhabitable portion 140, and the firstend in second direction Y of hollow member 30. Surrounding member 131,hollow member 30, and bacteria inhabitable portion 140 configure closingmeans 132 surrounding closed space 130. Hollow member 30 is not limitedin shape to the cylindrical shape, but can have a box shape with only asecond end in second direction Y being open. In this case, hollow member30 and bacteria inhabitable portion 140 configure closing means 132. Thenumber of the closed spaces 130 is not limited to two, but can be one,or greater than or equal to three.

Tube 18 serving as linking means (cylindrical member) is provided with afirst open portion 18 ab and a second open portion 18 ba that are apartfrom each other by a second distance L2 in an extending direction. Openportions 18 ab and 18 ba are provided at respective ends of tube 18according to the present embodiment. Open portions 18 ab and 18 ba arenot particularly limited insofar as open portions 18 ab and 18 ba arepositioned to link an anaerobic space 3 with an aerobic region 90 in awater cleaning system 1 to be described later (see FIG. 4). Openportions 18 ab and 18 ba can be provided not at the ends but at thecenter in the extending direction of tube 18. Tube 18 extends fromclosed space 130 provided with a first end 18 a in first direction Xthrough hollow member 30, bends at a right angle inside bacteriainhabitable portion 140, and has a second end 18 b that serves as anextending end projecting from a second surface 140 a in second directionY of bacteria inhabitable portion 140. First open portion 18 ab ispositioned to face closed space 130 whereas second open portion 18 ba ispositioned apart from bacteria inhabitable portion 140 by a firstdistance L1. The linking means can be embodied not only by tube 18 butalso by a cylindrical member such as a pipe to be described later. Tube18 and the pipe are not particularly limited in terms of theirmaterials, but can be made of vinyl chloride, ceramic, iron, glass, orrubber. When the linking means is made of vinyl chloride or ceramic,corrosion of the linking means can be inhibited for a long period oftime even in a case where seawater is used as breeding water to bedescribed later. The linking means preferably has a radius appropriatefor capacity of a retention tank to be described later, or the like.Tube 18 extends from each closed space 130 in the present embodiment.Each closed space 130 can alternatively be provided with a plurality oftubes 18. Tube 18, hollow member 30, meshed member 32, plate member 31,and surrounding member 131 are attached to bacteria inhabitable portion140 in water cleaning unit 100 as described above. Alternatively, atleast one of these members can be preliminarily fixed to bacteriainhabitable portion 140.

In a case where bacteria inhabitable portion 140 is defined as a firstbacteria inhabitable portion 140 as depicted in FIG. 3, a secondbacteria inhabitable portion 141 inhabitable by facultative anaerobicbacteria is attached so as to be adjacent to a second end in seconddirection Y of first bacteria inhabitable portion 140 and a thirdbacteria inhabitable portion 142 inhabitable by aerobic bacteria isattached so as to be adjacent to a second end in second direction Y ofsecond bacteria inhabitable portion 141. Second bacteria inhabitableportion 141 and third bacteria inhabitable portion 142 are formed bypressing to a certain degree a particulate carrier such as sand 50 intoa substantially rectangular shape in a plan view. Surrounding member 131is not provided on side surfaces of second bacteria inhabitable portion141 and third bacteria inhabitable portion 142 in the presentembodiment. Alternatively, the side surfaces of bacteria inhabitableportions 141 and 142 can be surrounded with surrounding member 131.Second bacteria inhabitable portion 141 and third bacteria inhabitableportion 142 can be preliminarily provided so as to be adjacent to firstbacteria inhabitable portion 140 or can be preliminarily provided to adifferent water cleaning unit to be described later.

In order to configure water cleaning system 1 according to the firstembodiment of the present invention so as to include water cleaning unit100, water cleaning unit 100 is mounted on an inner bottom surface 2 cof a retention tank (water tank) 2 made of transparent glass or acryl asdepicted in FIG. 4, coral sand 70 is then supplied on a surface thereof(on third bacteria inhabitable portion 142) to form aerobic region 90inhabitable by hydrosphere organisms (aquatic organisms) above a corallayer 7. In this case, coral sand 70 is accumulated only to a positionlower than second end 18 b of tube 18 so that second end 18 b of tube 18projects from coral layer 7 made of coral sand 70. Coral sand 70contains calcium carbonate (CaCO₃) as a component thereof. When calciumcarbonate elutes into breeding water 9 as depicted in FIG. 5, breedingwater 9 is adjusted to be alkaline. Coral sand 70 can have diameters ofabout 1 to 30 mm, and can be natural or artificial. In order to increasein amount of hydrogen sulfide that is to be reduced in toxicity in ahydrogen sulfide toxicity reducing region to be described later, watercleaning unit 100 can include bacteria inhabitable portion 140additionally provided with an iron component such as powdered iron, orsand 50 and the like can be mixed with an iron component. Subsequently,retention tank 2 is filled with breeding water 9 as depicted in FIG. 4,and water cleaning unit 100 and coral sand 70 are immersed in breedingwater 9. Saltwater fishes are bred as hydrosphere organisms in thepresent embodiment, and natural seawater or artificial seawater is usedas slightly alkaline breeding water 9. Opening 30 a of hollow member 30is closed by meshed member 32 with plate member 31 being interposedtherebetween. Accordingly, andosol 40 will not enter hollow member 30and hollow member 30 is filled with breeding water 9. First bacteriainhabitable portion 140 formed by preliminarily pressing andosol 40 intoa massive shape is thus installed in breeding water 9. Sand 50 is usedas a particulate carrier in the present embodiment. The particulatecarrier can be made of an artificial material such as plastic or can bewood chips, gravel, or the like insofar as the particulate carrier isinhabitable by aerobic bacteria and facultative anaerobic bacteria.Timing for filling retention tank 2 with breeding water 9 is not limitedto after supply of coral sand 70, but can be before mounting watercleaning unit 100, or after mounting water cleaning unit 100 and beforesupply of coral sand 70.

In a case where water cleaning unit 100 includes neither second bacteriainhabitable portion 141 nor third bacteria inhabitable portion 142preliminarily pressed to a certain degree, water cleaning unit 100 ismounted on inner bottom surface 2 c of retention tank 2. Thereafter,sand 50 (or gravel) and coral sand 70 are sequentially supplied on thesurface thereof and retention tank 2 is filled with breeding water 9(breeding water 9 can be filled before water cleaning unit 100 ismounted, or after water cleaning unit 100 is mounted and before sand 50or coral sand 70 is supplied), so that second bacteria inhabitableportion 141 inhabitable by facultative anaerobic bacteria is formedbelow the layer of sand 50 adjacent to first bacteria inhabitableportion 140 and third bacteria inhabitable portion 142 inhabitable byaerobic bacteria is formed thereabove. An exemplary amount of sand 50 tobe used is about one sixth to one eighth of the volume of breeding water9. Sand 50 can be collected at the bottom of the sea or the likeoriginally inhabited by aerobic bacteria and facultative anaerobicbacteria. In this case, these bacteria are likely to be settled in anaerobic layer 6 and a facultative anaerobic layer 5 during startup ofwater cleaning system 1 to be described later with a shorter period oftime required for the startup.

The linking means (tube 18) is provided to project upward from closedspace 130 in the present embodiment. Alternatively, the linking meanscan be provided to project downward, or can be provided to extendlaterally from closed space 130 and project from side surface 140 b offirst bacteria inhabitable portion 140. In a case where sand 50 and thelike are sequentially supplied to form second bacteria inhabitableportion 141 and third bacteria inhabitable portion 142 in such aconfiguration, a surrounding member covering side surfaces 140 b, lowersurface 140 c, and the like of first bacteria inhabitable portion 140preferably has the upper end positioned above upper surface 140 a offirst bacteria inhabitable portion 140 so as to prevent sand 50 and thelike from closing the second end of the tube. Sand 50 and the like areaccumulated in this surrounding member. Such a surrounding member can beprovided to indicate what amount of sand 50 and the like should besupplied. Instead of providing such a surrounding member, the tube orthe pipe can be made longer such that the second end is sufficientlyapart from side surface 140 b of first bacteria inhabitable portion 140.

After breeding water 9 is filled, hydrosphere organisms are bred inaerobic region 90 located at a second end in second direction Y of coralsand 70 to cause breeding water 9 to contain a certain amount of organicmatter derived from hydrosphere organisms. When such a state is kept fora certain period of time, third bacteria inhabitable portion 142, whichreceives light from above and from the lateral sides and has an aerobicenvironment with entry of oxygen dissolved in breeding water 9,configures aerobic layer 6 to multiply a plurality of types of aerobicbacteria inhabitable under an aerobic condition. Examples of the organicmatter derived from hydrosphere organisms include excrement and deadbodies of hydrosphere organisms. Examples of aerobic bacteria includesulfur oxidizing bacteria such as photosynthetic sulfur bacteria,photosynthetic bacteria, and nitrifying bacteria. Aerobic bacteriainhabiting aerobic layer 6 consume oxygen in breeding water 9 and theamount of oxygen gradually decreases toward the bottom in the layer ofsand 50, so that second bacteria inhabitable portion 141 has ananaerobic environment with no or little oxygen and facultative anaerobiclayer 5 is generated. Facultative anaerobic layer 5 receives littlelight due to blockage by aerobic layer 6, so that a plurality of typesof facultative anaerobic bacteria, which are habitable under an aerobiccondition as well as under an anaerobic environment, multiply. Examplesof facultative anaerobic bacteria include sulfur oxidizing bacteria suchas colorless sulfur bacteria, and nitrate-reducing bacteria.

First bacteria inhabitable portion 140 having a flat surface is providedwith second bacteria inhabitable portion 141 and third bacteriainhabitable portion 142 at the second end in second direction Y, andlight from the lateral sides and from below is blocked by andosol 40.First bacteria inhabitable portion 140 thus has an anaerobic environmentwith no light received and no oxygen contained, and an obligatoryanaerobic layer 4 is generated. Accordingly, a plurality of types ofobligatory anaerobic bacteria, which are inhabitable under an anaerobiccondition, multiply. Examples of obligatory anaerobic bacteria include aplurality of types of sulfate-reducing bacteria B (see FIG. 5) that caninhabit obligatory anaerobic layer 4 as well as facultative anaerobiclayer 5 and act differently. Sulfate-reducing bacteria B are mostactivated under a slightly alkaline environment. The number ofinhabiting obligatory anaerobic bacteria in a surface portion ofobligatory anaerobic layer 4 in contact with retention tank 2 (a portionblocking light transmitted through retention tank 2) is relativelysmaller than that of the interior of obligatory anaerobic layer 4. Firstbacteria inhabitable portion 140 is made of andosol 40 that isoriginally inhabited by sulfate-reducing bacteria B. Sulfate-reducingbacteria B can multiply in first bacteria inhabitable portion 140 in arelatively short period of time to form obligatory anaerobic layer 4.Closed space 130 configures anaerobic space 3 having an anaerobicenvironment with no light received and no oxygen contained. Tube 18directly links anaerobic space 3 and aerobic region 90. Aerobicbacteria, facultative anaerobic bacteria, and obligatory anaerobicbacteria sequentially multiply in this manner to generate chainedcirculation of microorganisms. Water cleaning system 1 is thus formed asa breeding system for hydrosphere organisms in the present embodiment.Retention tank 2 is preferably provided thereabove with a water tank airpump (not depicted) for supplying breeding water 9 with oxygen.Anaerobic space 3 is preferably made larger as retention tank 2 haslarger capacity. The amount of andosol 40 configuring obligatoryanaerobic layer 4 is preferably about one sixth to one eighth of thevolume of breeding water 9, for example.

In water cleaning system 1 thus configured, aerobic region 90 includingorganic matter derived from hydrosphere organisms and oxygen ispositioned to link with third bacteria inhabitable portion 142 via corallayer 7. When the organic matter derived from hydrosphere organisms bredin breeding water 9 passes through coral layer 7 and is deposited on thesurface of aerobic layer 6, the organic matter is decomposed by aerobicbacteria in aerobic layer 6 and is then decomposed by facultativeanaerobic bacteria in facultative anaerobic layer 5 provided belowaerobic layer 6. As described above, the plurality of types of aerobicbacteria and facultative anaerobic bacteria inhabit layers 5 and 6,respectively. Among these, nitrifying bacteria serving as aerobicbacteria and nitrate-reducing bacteria serving as facultative anaerobicbacteria, for example, decompose toxic ammonia (NH₃) initially intonitrite ions (NO₂ ⁻) and nitrate ions (NO₃ ⁻) and then into innocuousnitrogen (N₂), as depicted in FIG. 5. This is reaction calledheterotropic denitrification or simply called denitrification.Facultative anaerobic layer 5 intakes nitrate ions that are generated bypart of sulfate-reducing bacteria B having moved from obligatoryanaerobic layer 4 in the process of heterotropic denitrification, andsulfate-reducing bacteria B emit elemental sulfur (SO) and hydrogen ions(H⁺). This is called autotropic denitrification or sulfurdenitrification. In a case where breeding water 9 is neutralized oracidified by the hydrogen ions, sulfate-reducing bacteria B may bedeteriorated in action or damage hydrosphere organisms that prefer aslightly alkaline environment. However, hydrogen ions are neutralized bycalcium carbonate eluted from coral sand 70. At an initial stage afterthe start of water cleaning system 1, ammonia is decomposed mainly intonitrogen by heterotropic denitrification. However, autotropicdenitrification gradually becomes dominant, and ammonia will bedecomposed mainly by autotropic denitrification after elapse of severalyears from the start of water cleaning system 1. Furthermore, phosphoricacid and the like, which have been removed using a conventionally knownfiltration device or through processes of replacing water and sand, aredecomposed by different types of aerobic bacteria and facultativeanaerobic bacteria.

Decomposed matter and the like by these aerobic bacteria and facultativeanaerobic bacteria infiltrate obligatory anaerobic layer 4 due to theeffect of negatively-charged colloidal particles in andosol 40, and aredecomposed by obligatory anaerobic bacteria in obligatory anaerobiclayer 4. A plurality of obligatory anaerobic bacteria inhabit obligatoryanaerobic layer 4 as described above, and part of sulfate-reducingbacteria B generate hydrogen sulfide (H₂S) from sulfur compoundscontaining sulfate ions (SO₄ ²⁻) as depicted in FIG. 5. Obligatoryanaerobic layer 4 links with anaerobic space 3 via meshed member 32 andplate member 31. Part of hydrogen sulfide thus generated andsulfate-reducing bacteria B move from obligatory anaerobic layer 4 toanaerobic space 3 through meshed member 32 and plate member 31. Inobligatory anaerobic layer 4, part of hydrogen sulfide reacts with ironoxide (FeO) to generate iron sulfide (FeS) that is less toxic. Suchreaction occurs also in anaerobic space 3 and aerobic region 90. Inanaerobic space 3, elemental sulfur generated by autotropicdenitrification reacts with iron sulfide to generate iron disulfide(FeS₂) as depicted in FIG. 5. Iron disulfide is gradually solidified, sothat a substance containing iron disulfide as a component and callediron pyrites or pyrite is accumulated in anaerobic space 3 for tens ofyears. Such reaction occurs also in obligatory anaerobic layer 4.Colorless sulfur bacteria generate sulfuric acid (H₂SO₄) from hydrogensulfide in facultative anaerobic layer 5 as depicted in FIG. 5, so thathydrogen sulfide is reduced in toxicity also in this manner. Suchreaction occurs also in obligatory anaerobic layer 4. Andosol 40originally contains an iron component. Hydrogen sulfide also reacts withthis iron component to generate iron sulfide. In a case wherefacultative anaerobic layer 5, aerobic layer 6, and the like furthercontain an iron component or a different metal component, such acomponent may absorb or reduce in toxicity toxic substances such ashydrogen sulfide.

Part of sulfate-reducing bacteria B and hydrogen sulfide having movedfrom obligatory anaerobic layer 4 to anaerobic space 3 pass through tube18 to reach aerobic region 90 along with a slight stream generated byorganic matter and the like infiltrating lower layers 4 to 6. Asdescribed earlier, hydrogen sulfide reacts with iron oxide in aerobicregion 90 to generate iron sulfide. Although hydrogen sulfide is a toxicsubstance, it is discharged little by little from tube 18 and quicklyreacts with iron oxide to generate less toxic iron sulfide. Accordingly,hydrogen sulfide will not damage hydrosphere organisms in aerobic region90. Sulfate-reducing bacteria B having moved to aerobic region 90 bondwith iron sulfide as depicted in FIG. 5 and are then deposited on thesurfaces of coral layer 7 and aerobic layer 6. Sulfate-reducing bacteriaB are obligatory anaerobic bacteria and cannot inhabit under an aerobiccondition as described above. Iron sulfide reacts quite well withoxygen. Accordingly, sulfate-reducing bacteria B provided on surfacesthereof with iron sulfide are not affected by oxygen but are convertedto be inhabitable even under an aerobic condition. Sulfate-reducingbacteria B acts to decompose organic matter if there is much organicmatter nearby to be decomposed, whereas sulfate-reducing bacteria Bcomes into a dormant state if there is little organic matter nearby.Sulfate-reducing bacteria B in the dormant state restart activity iforganic matter increases in amount. Hydrogen sulfide having moved toaerobic region 90 does not entirely react with iron sulfide, but part ofhydrogen sulfide reacts with oxygen (O₂) in aerobic layer 6 as depictedin FIG. 5 to generate sulfuric acid that can be dissolved in breedingwater 9 to become sulfate ions, or the remaining hydrogen sulfidereaches aerobic layer 6 or facultative anaerobic layer 5 withoutreacting. Iron sulfide in aerobic region 90 does not entirely bond withsulfate-reducing bacteria B, but part of the iron sulfide may beconverted to sulfate ions or iron disulfide due to action of respectivebacteria. Photosynthetic bacteria generates, from hydrogen sulfide,different sulfur compounds less toxic than hydrogen sulfide in aerobicregion 90, coral layer 7, or aerobic layer 6, so that hydrogen sulfideis reduced in toxicity. In water cleaning system 1, organic matter isbiologically filtered in the three steps by activity of bacteriarespectively in aerobic layer 6, facultative anaerobic layer 5, andobligatory anaerobic layer 4 to be reduced in toxicity and circulate inretention tank 2. Furthermore, a hydrogen sulfide toxicity reducingregion 143 (see FIG. 4) is artificially formed in a short period oftime, where hydrogen sulfide can be reduced in toxicity by activity ofbacteria and the like in at least any one of aerobic region 90, corallayer 7, aerobic layer 6, facultative anaerobic layer 5, obligatoryanaerobic layer 4, and anaerobic space 3. Breeding water 9 containingsuch organic matter has a cleaning effect substantially equal to anatural cleaning effect (at the bottom of the sea, for example).

Obligatory anaerobic layer 4 may be further provided thereabove with ananaerobic layer for biological filtering in the four steps, depending onthicknesses of layers 4 to 6, the amount of dissolved oxygen, and thelike. Water cleaning system 1 configured identically may have bacteriaof different types and the like multiplying in the respective layers.Depending on the types and the like of bacteria thus multiplied, atleast any one of these mechanisms for reduction in toxicity of hydrogensulfide may not function or hydrogen sulfide may be reduced in toxicityby a mechanism other than those described above.

Water cleaning system 1 according to the present embodiment can beconstructed not by including water cleaning unit 100 but by including astructure corresponding to water cleaning unit 100 in breeding water 9.However, in the case where no water cleaning unit 100 is provided, asufficient number of hydrosphere organisms cannot be bred from thebeginning. The startup process is preferably performed for about severalmonths so that bacteria can be settled respectively in layers 4 to 6 andorganic matter can circulate stably. Specifically, in place of watercleaning unit 100, hollow member 30, to which plate member 31 and meshedmember 32 are attached, and a cylindrical member such as tube 18, areinstalled on inner bottom surface 2 c of retention tank 2, andosol 40,sand 50, and coral sand 70 are sequentially supplied thereon, andretention tank 2 is filled with breeding water 9, so as to achieve thestate depicted in FIG. 4. In this case, sand 50 is preferably collectedat the bottom of the sea or the like originally inhabited by aerobicbacteria and facultative anaerobic bacteria, for example. These bacteriaare thus likely to be settled in aerobic layer 6 and facultativeanaerobic layer 5 during startup of water cleaning system 1 with ashorter period of time required for the startup.

In order to start up water cleaning system 1 in such a state, gas supplymeans 80 as in FIG. 4 is initially attached to the cylindrical member asdepicted in FIG. 6 (step S1). Gas supply means 80 is preferably attachedas low as possible in a range above obligatory anaerobic layer 4. Gassupply means 80 can be attached when sand 50 is accumulated on thesurface of andosol 40 configuring obligatory anaerobic layer 4.Hydrosphere organisms are released in aerobic region 90 in retentiontank 2 and light is applied to retention tank 2 at least from abovethrereof. The processes of releasing hydrosphere organisms and applyinglight are performed in an appropriate step, and can be performed priorto step S1, for example. The number of hydrosphere organisms released inretention tank 2 at this stage is made smaller than the breedable numberin water cleaning system 1 having been started up. Retention tank 2 canbe irradiated with light from above using a light source such as afluorescent lamp (not depicted). Retention tank 2 can be alternativelyplaced at a place receiving sunlight, so that light is applied thereto.Still alternatively, retention tank 2 can be supplied with organicmatter derived from organisms, instead of releasing hydrosphereorganisms.

Subsequently started is supply of air from gas supply means 80 to thecylindrical member (step S2). Breeding water 9 in the cylindrical memberis thus gradually pressed upward by air. The cylindrical member is thusprovided therein with a stream from anaerobic space 3 toward aerobicregion 90 and air is discharged from the cylindrical member as smallbubbles. The cylindrical member is thus provided outside thereof with astream from aerobic region 90 toward obligatory anaerobic layer 4. Gassupplied from gas supply means 80 is not limited to air insofar as thegas is not toxic.

This state is kept and size of the bubbles discharged from thecylindrical member is observed for a predetermined period of time (e.g.about three to six months) to visually determine whether or not thebubbles discharged from the cylindrical member are increased in size andpredetermined size of bubbles are discharged (step S3). Sand 50configuring aerobic layer 6 and facultative anaerobic layer 5 andandosol 40 configuring obligatory anaerobic layer 4 are pressed by thedownward stream during the above period of time, so that breeding water9 becomes unlikely to infiltrate obligatory anaerobic layer 4.Accordingly, oxygen and incident light are gradually decreased in amounttoward downward from aerobic layer 6. Furthermore, aerobic bacteria,facultative anaerobic bacteria, and obligatory anaerobic bacteriamultiply in aerobic layer 6, facultative anaerobic layer 5, andobligatory anaerobic layer 4, respectively. Breeding water 9 flowinginside the cylindrical member decreases, whereas air supplied from gassupply means 80 is unlikely to flow upward, is clogged halfway, and isdischarged as larger bubbles from the cylindrical member. If bubbles ofpredetermined size are not discharged from the cylindrical member (NO instep S3), andosol 40 is determined as not being sufficiently pressed andthe above state is kept. If bubbles of the predetermined size aredischarged from the cylindrical member after elapse of several months(YES in step S3), andosol 40 is determined as being sufficiently pressedand supply of air to the cylindrical member is stopped (step S4).Bacteria most appropriate for environments in layers 4 to 6 are settledin layers 4 to 6 at this stage, and the startup of water cleaning system1 is completed by detaching gas supply means 80 from the cylindricalmember (step S5). Such a startup process is preferably performed forabout several months.

Gas supply means 80 can be replaced with a pump and breeding water 9 canbe sucked from second end 18 b (see FIG. 4) of the cylindrical membersuch as tube 18 so as to generate a stream from anaerobic space 3 towardaerobic region 90 in the cylindrical member. Even in a case where such astartup process is not performed but water cleaning system 1 is startedwith a limited number of hydrosphere organisms, sand 50 and andosol 40are gradually pressed and the respective bacteria multiply and aresettled gradually in layers 4 to 6. Accordingly, the startup process isnot essential in this case.

As depicted in FIG. 7, water cleaning unit 100 can be provided with asupport leg 551 securing a predetermined gap G from retention tank 2serving as an installation surface 552 or different water cleaning unit100. Support leg 551 in water cleaning unit 100 depicted in this figureextends from a lower surface 550 a of water cleaning unit 100. Supportleg 551 can alternatively be provided to extend from an upper surface550 b or a side surface 550 c. Alternatively, lower surface 550 a orupper surface 550 b of water cleaning unit 100 can be recessed acrossside surface 550 c at a portion corresponding to second end 18 b of tube18 in different water cleaning unit 100, so that a plurality of watercleaning units 100 can be appropriately stacked similarly to the case ofproviding support leg 551. Still alternatively, a support leg can beprovided to a different water cleaning unit to be described later or asurface of a different water cleaning unit can be recessed as describedabove. The different water cleaning unit and water cleaning unit 100 canbe stacked together.

As depicted in FIG. 4, the linking means (tube 18) is entirely providedinside retention tank 2 in water cleaning system 1 according to thepresent embodiment. Alternatively, the linking means extending fromanaerobic space 3 can penetrate a side surface 2 a of retention tank 2,extend upward outside retention tank 2, and penetrate side surface 2 aof retention tank 2 again to reach aerobic region 90. The same appliesto water cleaning systems 210 and 750 to be described later.

If meshed member 32 is strong enough to be durable against weight ofobligatory anaerobic layer 4, facultative anaerobic layer 5, aerobiclayer 6, and the like, meshed member 32 can be mounted directly on theupper surface of hollow member 30 without plate member 31 beinginterposed therebetween.

Furthermore, in water cleaning system 1, first bacteria inhabitableportion 140, to which surrounding member 131 is not attached, can beinstalled on inner bottom surface 2 c of retention tank 2 to form theclosed space. In this case, retention tank 2 and water cleaning unit 100configure closed space forming means for forming the closed space. Ifandosol 40 of first bacteria inhabitable portion 140 does not loosen,there is no need to provide at least any one of hollow member 30, platemember 31, and meshed member 32.

As described above, water cleaning system 1 according to the firstembodiment of the present invention includes aerobic region 90 includingbreeding water 9 containing organic matter derived from hydrosphereorganisms and oxygen, aerobic layer 6 linking with aerobic region 90 andinhabited by aerobic bacteria, facultative anaerobic layer 5 providedadjacent to aerobic layer 6 and inhabited by facultative anaerobicbacteria, obligatory anaerobic layer 4 provided adjacent to facultativeanaerobic layer 5, inhabited by obligatory anaerobic bacteria, and madeof andosol 40, anaerobic space 3 having an anaerobic environment,allowing the obligatory anaerobic bacteria inhabiting obligatoryanaerobic layer 4 and products therefrom to flow therein, and tube 18 aslinking means linking anaerobic space 3 and aerobic region 90.

In water cleaning system 1 thus configured, organic matter in breedingwater 9 reaches aerobic layer 6 and subsequently reaches facultativeanaerobic layer 5, to be decomposed by aerobic bacteria and facultativeanaerobic bacteria respectively inhabiting the layers. Decomposed matterthus obtained subsequently reaches obligatory anaerobic layer 4 and isdecomposed by obligatory anaerobic bacteria. At this stage,sulfate-reducing bacteria B serving as obligatory anaerobic bacteriagenerate hydrogen sulfide from sulfur compounds. Hydrogen sulfide thusgenerated is reduced in toxicity in hydrogen sulfide toxicity reducingregion 143 that is formed in at least one of aerobic region 90, aerobiclayer 6, facultative anaerobic layer 5, obligatory anaerobic layer 4,and anaerobic space 3. Specifically, hydrogen sulfide is reduced intoxicity by reacting with an iron component in breeding water 9 whilemoving to aerobic region 90 together with sulfate-reducing bacteria B toform iron sulfide (FeS) less toxic to hydrosphere organisms thanhydrogen sulfide, or by being converted to different sulfur compoundsless toxic to hydrosphere organisms than hydrogen sulfide by sulfuroxidizing bacteria, photosynthetic bacteria, and the like inhabitinghydrogen sulfide toxicity reducing region 143. Sulfate-reducing bacteriaB having moved to aerobic region 90 become inhabitable even in anaerobic environment by reaction with iron sulfide. Sulfate-reducingbacteria B reach the surface of the aerobic layer and decompose organicmatter if the organic matter therein is relatively large in amount butcome into a dormant state if the organic matter therein is relativelysmall in amount so as to increase the amount of organic matter to bedecomposed. Decomposition of organic matter derived from hydrosphereorganisms and contained in breeding water 9 as well as reduction intoxicity of hydrogen sulfide generated through the decomposition asdescribed above can inhibit accumulation of toxic matter in retentiontank 2 neither with a separate device for supplementing a filteringfunction nor with processes of replacing water and sand semipermanentlyor for a long period of time, and can clean breeding water 9 inretention tank 2. Furthermore, there is no need to reduce the number ofbred hydrosphere organisms even after hydrosphere organisms have grownbut the number of breedable hydrosphere organisms can be increased incomparison to a conventional case.

Opening 30 a of hollow member 30 having the open top is closed by meshedmember 32 that has water permeability and blocks passage of andosol 40.The peripheries of hollow member 30 and meshed member 32 are coveredwith andosol 40 to form anaerobic space 3 inside hollow member 30.Anaerobic space 3 can thus be easily formed and be kept for a longperiod of time.

Furthermore, sulfate-reducing bacteria B originally inhabit andosol 40.Obligatory anaerobic layer 4 made of andosol 40 allows sulfate-reducingbacteria B to multiply easily and reliably so as to form obligatoryanaerobic layer 4 that can decompose a sufficient amount of organicmatter.

Aerobic layer 6 is provided on the surface with coral layer 7 made ofcoral sand 70, so that calcium carbonate elutes from coral sand 70 tokeep breeding water 9 slightly alkaline similarly to seawater.Accordingly, the interior of retention tank 2 can be kept in anenvironment appropriate for breeding of saltwater fishes, anddeterioration in activity of sulfate-reducing bacteria B can beinhibited.

A water quality conditioning agent containing calcium carbonate,eggshell, a substance similarly having a function of eluting a calciumcarbonate component into breeding water 9, or the like can replace orcan be provided along with coral sand 70. Alternatively, the waterquality conditioning agent, the eggshell, or the like can be provided toadjust neutralized or acidified breeding water 9 to be slightlyalkaline. Breeding water 9 is neutralized or acidified because retentiontank 2 contains a large or extremely small amount of organic matter suchas excrement, for example. If a large amount of organic matter iscontained, decomposition of the organic matter can be promoted byadjusting breeding water 9 to be slightly alkaline. It is possible toactivate again sulfate-reducing bacteria B having significantlydeteriorated decomposing ability due to an extremely small amount oforganic matter. In a case where retention tank 2 is likely to receive anacid substance, e.g. when retention tank 2 placed outdoors tends toreceive acid rain, it is preferred to preliminarily add the waterquality conditioning agent, the eggshell, or the like.

A water cleaning method according to the first embodiment of the presentinvention is adopted as a method of breeding hydrosphere organisms. Themethod includes installing, in breeding water 9, first bacteriainhabitable portion 140 in a massive shape obtained by preliminarilypressing andosol 40 serving as a soil material inhabitable by obligatoryanaerobic bacteria, forming, in breeding water 9, second bacteriainhabitable portion 141 that is adjacent to first bacteria inhabitableportion 140, has sand 50 as a particulate carrier, and is inhabitable byfacultative anaerobic bacteria, third bacteria inhabitable portion 142that is adjacent to second bacteria inhabitable portion 141, has sand50, and is inhabitable by aerobic bacteria, anaerobic space 3 that hasan anaerobic environment and links with first bacteria inhabitableportion 140, positioning to link with third bacteria inhabitable portion142, aerobic region 90 including organic matter derived from hydrosphereorganisms and oxygen, linking aerobic region 90 and anaerobic space 3,thus forming obligatory anaerobic layer 4 by multiplying obligatoryanaerobic bacteria in first bacteria inhabitable portion 140, formingfacultative anaerobic layer 5 by multiplying facultative anaerobicbacteria in second bacteria inhabitable portion 141, forming aerobiclayer 6 by multiplying aerobic bacteria in third bacteria inhabitableportion 142, causing these bacteria to decompose the organic matter, andmoving obligatory anaerobic bacteria flowing out of first bacteriainhabitable portion 140 and products therefrom from anaerobic space 3 toaerobic region 90.

In accordance with such a water cleaning method, aerobic region 90including bred hydrosphere organisms or the like and organic matterderived from hydrosphere organisms is positioned to link with thirdbacteria inhabitable portion 142 so that aerobic region 90 and anaerobicspace 3 link with each other. Accordingly, obligatory anaerobic bacteriamultiply in first bacteria inhabitable portion 140 to form obligatoryanaerobic layer 4, facultative anaerobic bacteria multiply in secondbacteria inhabitable portion 141 to form facultative anaerobic layer 5,and aerobic bacteria multiply in third bacteria inhabitable portion 142to form aerobic layer 6. Similarly to water cleaning system 1 accordingto the present invention, decomposition of organic matter derived fromhydrosphere organisms and contained in water as well as reduction intoxicity of hydrogen sulfide generated through the decomposition canthus inhibit accumulation of toxic matter derived from the organicmatter in retention tank 2 neither with a separate device forsupplementing a filtering function nor with processes of replacing waterand sand semipermanently or for a long period of time. Furthermore,there is no need to reduce the number of bred hydrosphere organisms evenafter hydrosphere organisms have grown but the number of breedablehydrosphere organisms can be increased in comparison to a conventionalcase. Furthermore, provision of first bacteria inhabitable portion 140preliminarily pressed into a massive shape enables artificial formationof a decomposition cycle of organic matter for causing the reduction intoxicity of hydrogen sulfide at a desired position in a short period oftime.

In order to start up water cleaning system 1, using tube 18 serving as acylindrical member embodying the linking means, light is applied toaerobic layer 6 and gas is supplied from gas supply means 80 into tube18 in the state where a breeding space 90 includes organic matterderived from organisms so as to cause a stream from anaerobic space 3toward above aerobic layer 6 in tube 18 and keep this state for apredetermined period of time.

Breeding water 9 in tube 18 thus flows upward toward breeding space 90,so that breeding water 9 flows downward toward aerobic layer 6,facultative anaerobic layer 5, and obligatory anaerobic layer 4. Sand 50configuring aerobic layer 6 and facultative anaerobic layer 5 andandosol 40 configuring obligatory anaerobic layer 4 are pressed by thedownward stream, breeding water 9 passing through layers 4 to 6 isgradually reduced and lower layers 5 and 6 have a less amount of oxygenand a less amount of incident light. Accordingly, layers 4 to 6 haveenvironments appropriate for inhabitation by aerobic bacteria,facultative anaerobic bacteria, and obligatory anaerobic bacteria,respectively, and these bacteria are sufficiently settled in layers 4 to6. Water cleaning system 1 can thus be started up stably.

Water cleaning unit 100 is used to achieve the water cleaning method andwater cleaning system 1. Water cleaning unit 100 includes bacteriainhabitable portion 140 made of andosol 40, having a massive shape, andinhabitable by obligatory anaerobic bacteria, closed space 130surrounded with closing means 132 at least partially configured bybacteria inhabitable portion 140, and tube 18 as a cylindrical memberthat has first open portion 18 ab and second open portion 18 ba, has alength so as to extend from closed space 130 through closing means 132,with second open portion 18 ba being positioned apart from bacteriainhabitable portion 140 by first distance L1 when first open portion 18ab is positioned to face closed space 130.

In this configuration, second open portion 18 ba of tube 18 ispositioned apart from bacteria inhabitable portion 140 by first distanceL1 when first open portion 18 ab is positioned to face closed space 130.Accordingly, aerobic region 90, aerobic layer 6, facultative anaerobiclayer 5, obligatory anaerobic layer 4, and anaerobic space 3 linkingwith aerobic region 90 can be easily formed with second open portion 18ba not closed by sand 50 and the like when sand 50 and the like aresupplied to form aerobic layer 6 and facultative anaerobic layer 5 onsecond surface 140 a provided with tube 18 projecting therefrom, insecond direction Y of bacteria inhabitable portion 140. When watercleaning unit 100 is immersed in breeding water 9 containing organicmatter derived from hydrosphere organisms, closed space 130 configuresanaerobic space 3 having an anaerobic environment and obligatoryanaerobic bacteria and products therefrom can move from first openportion 18 ab toward second open portion 18 ba. Use of water cleaningunit 100 enables easy formation of first bacteria inhabitable portion140 obtained by pressing andosol 40 into a massive shape in breedingwater 9, and reduction in startup period of time for achievingsufficient decomposition of organic matter as depicted in FIG. 5.

In bacteria inhabitable portion 140, surrounding member 131 blockingpassage of a soil material covers both surfaces 140 b in first directionX as the surfaces with no tube 18 projecting therefrom and first surface140 c in second direction Y. This configuration can inhibit crumbling ofbacteria inhabitable portion 140 due to loosening of the soil materialand flowing of the soil material out of water cleaning unit 100 immersedin breeding water 9.

Surrounding member 131 further has a light shielding property so as toprevent without time or effort light from entering closed space 130 inwater cleaning system 1 that includes water cleaning unit 100 andtypically used transparent retention tank 2.

Water cleaning unit 100 is provided, between first bacteria inhabitableportion 140 and closed space 130, with meshed member 32 having waterpermeability and blocking passage of andosol 40, so as to inhibitandosol 40 from entering closed space 130 (anaerobic space 3).

There is further included sand 50 as a particulate carrier inhabitableby aerobic bacteria and facultative anaerobic bacteria in order to formsecond bacteria inhabitable portion 141 that is adjacent to firstbacteria inhabitable portion 140 inhabitable by obligatory anaerobicbacteria and is inhabitable by facultative anaerobic bacteria, and thirdbacteria inhabitable portion 142 that is adjacent to second bacteriainhabitable portion 141 and inhabitable by aerobic bacteria. Use ofwater cleaning unit 100 thus configured eliminates necessity forsupplying sand 50 and the like to form aerobic layer 6 and facultativeanaerobic layer 5 as depicted in FIG. 4. This can reduce time and effortfor forming water cleaning system 1. The particulate carrier used forforming each of aerobic layer 6 and facultative anaerobic layer 5 can beof a different type.

At least bacteria inhabitable portion 140 is dry in water cleaning unit100, to achieve reduction in weight and facilitate delivery.

Water cleaning unit 100 includes support leg 551 securing predeterminedgap G between retention tank 2 serving as installation surface 552 anddifferent water cleaning unit 100. A plurality of water cleaning units100 can be stacked and installed without closing second end 18 b of tube18. Furthermore, organic matter and oxygen in breeding water 9 cansufficiently enter aerobic layer 6 of different water cleaning unit 100located at a first end in second direction Y. As the number of watercleaning units 100 increases in this manner, organic matter to bedecomposed can be increase in amount and decomposing ability can beimproved. Furthermore, water cleaning unit 100 can be easily locatedhorizontally even in a case where the bottom of the sea, the bottom of ariver, or the like to be mounted with water cleaning unit 100 is unevento some extent due to rocks or the like.

Second Embodiment

The second embodiment according to the present invention will now bedescribed next with reference to FIGS. 8 to 10. Those members similar inshape, material, and the like will be denoted by identical referencesigns and will not be described repeatedly.

As depicted in FIG. 8, water cleaning unit 200 according to thisembodiment is provided with cylindrical member insertion holes 202 a,203 b, and 204 b as penetrating portions penetrating in second directionY (vertically in the present embodiment) a bacteria inhabitable portion202 made of a soil material, having a massive shape, and inhabitable byobligatory anaerobic bacteria, a meshed member 203, and a plate member204. In order to use water cleaning unit 200, plate member 204 havingsubstantially rectangular shape and a second (upper) surface in seconddirection Y (in the vertical direction in the present embodiment)entirely covered with meshed member 203 is attached to bacteriainhabitable portion 202, and a pipe 206 having a linear shape in a sideview and serving as linking means (cylindrical member) is inserted tocylindrical member insertion holes 202 a, 203 b, and 204 b. Pipe 206 isprovided with a first open portion 206 ab and a second open portion 206ba apart from each other by second distance L2 in the extendingdirection. Open portions 206 ab and 206 ba are provided at therespective ends in the present embodiment. First open portion 206 ab ispositioned to face a first end of bacteria inhabitable portion 202whereas second open portion 206 ba projects from bacteria inhabitableportion 202 at a second end of bacteria inhabitable portion 202 and ispositioned apart from bacteria inhabitable portion 202 by first distanceL1. A plurality of support means 205 in pillar shapes depicted in FIG. 9is attached to a first end in second direction Y (the lower side in thepresent embodiment) of plate member 204. Furthermore, surrounding member131 is provided to be in contact with both surfaces 202 b in firstdirection X (in the horizontal direction in the present embodiment) ofbacteria inhabitable portion 202 that is provided adjacent to a secondend in second direction Y of meshed member 203, both end surfaces 203 ain first direction X of meshed member 203, both end surfaces 204 a infirst direction X of plate member 204 and a first surface 205 a insecond direction Y of support means 205. Bacteria inhabitable portion202 and surrounding member 131 thus configure closing means 132 to forma closed space 201 surrounded with bacteria inhabitable portion 202 andsurrounding member 131. Pipe 206 extends from closed space 201 throughplate member 204, meshed member 203, and bacteria inhabitable portion202. Open portions 206 ab and 206 ba of pipe 206 are not particularlylimited insofar as open portions 206 ab and 206 ba are provided atpositions allowing an anaerobic space 213 and aerobic region 90 to linkwith each other in water cleaning system 210 to be described later (seeFIG. 10). Open portions 206 ab and 206 ba can be provided not at theends but at the center in the extending direction of pipe 206. Platemember 204 is made of a material similar to that for plate member 31according to the first embodiment, and meshed member 203 is made of amaterial similar to that for meshed member 32 according to the firstembodiment. A pipe 206 can be inserted so as to penetrate bacteriainhabitable portion 202 as in the present embodiment, or can be insertedonly halfway to bacteria inhabitable portion 202.

After water cleaning unit 200 is mounted on inner bottom surface 2 c ofretention tank 2 as depicted in FIG. 10, sand 50 (or gravel) and coralsand 70 are sequentially accumulated on the surface of bacteriainhabitable portion 202 and retention tank 2 is further filled withbreeding water 9. A nontransmissive portion 102 is provided at a lowerportion of side surface 2 a and on bottom surface 2 b of retention tank2 so as to prevent light from entering closed space 201. Nontransmissiveportion 102 can be provided by attaching a tape, a seal, or the like inblack to the lower portion of side surface 2 a and to bottom surface 2 bof retention tank 2. In a case where retention tank 2 hasnontransmittivity, there is no need to provide nontransmissive portion102. By keeping the state where breeding water 9 contains organic matterderived from hydrosphere organisms for a certain period of time,obligatory anaerobic bacteria multiply in bacteria inhabitable portion(first bacteria inhabitable portion) 202 to form an obligatory anaerobiclayer 207. Facultative anaerobic bacteria multiply in a lower portion ofthe layer of sand 50 (a second bacteria inhabitable portion 208) to formfacultative anaerobic layer 5 whereas aerobic bacteria multiply in anupper portion (a third bacteria inhabitable portion 209) to form aerobiclayer 6. Closed space 201 is brought into an anaerobic environment so asto configure anaerobic space 213.

With use of water cleaning unit 200 in this manner, it is possible toform water cleaning system 210 according to the second embodiment of thepresent invention including coral layer 7, aerobic layer 6, facultativeanaerobic layer 5, and obligatory anaerobic layer 207 that are formedfrom above, as well as anaerobic space 213 formed below obligatoryanaerobic layer 207 and aerobic region 90 linked with each other by pipe206. Water cleaning system 210 thus configured can circulate organicmatter and exert the effects similarly to water cleaning system 1depicted in FIG. 4 and described earlier. Furthermore, hydrogen sulfidecan be reduced in toxicity in aerobic region 90, aerobic layer 6,facultative anaerobic layer 5, obligatory anaerobic layer 207, andanaerobic space 213, each serving as hydrogen sulfide toxicity reducingregion 143.

In water cleaning unit 200 provided with neither support means 205 norsurrounding member 131, a plurality of pillar members serving as closedspace forming means can be provided on inner bottom surface 2 c ofretention tank 2 that also serves as closed space forming means forforming closed space 201 along with water cleaning unit 200, and watercleaning unit 200 can be installed in retention tank 2, so that platemember 204 is lifted upward from inner bottom surface 2 c by the pillarmembers and closed space 201 as depicted in FIG. 10 is formed at a firstend in second direction Y of bacteria inhabitable portion 202. In thiscase, retention tank 2 is preferred to be provided with nontransmissiveportion 102 as depicted in this figure or have a light shieldingproperty. Closed space 201 provided at the first end in second directionY of bacteria inhabitable portion 202 configures anaerobic space 213when water cleaning system 210 is formed by accumulating sand 50 and thelike at a second end in second direction Y of a water cleaning unit 250and filling retention tank 2 with breeding water 9. If andosol 40 inbacteria inhabitable portion 202 does not loosen in water cleaning unit250, neither plate member 204 nor meshed member 203 may be provided.

As described above, water cleaning unit 200 includes bacteriainhabitable portion 202 made of andosol 40, having a massive shape, andinhabitable by obligatory anaerobic bacteria, and pipe 206 as acylindrical member that has first open portion 206 ab and second openportion 206 ba and has a length to extend from the first end to thesecond end of bacteria inhabitable portion 202, with second open portion206 ba positioned apart from bacteria inhabitable portion 202 by firstdistance L1 at the second end of bacteria inhabitable portion 202 whenfirst open portion 206 ab is positioned to face the first end ofbacteria inhabitable portion 202.

In such a configuration, the water cleaning unit 200 is immersed inbreeding water 9 containing organic matter derived from hydrosphereorganisms, and sand 50 and the like are supplied to form aerobic layer 6and facultative anaerobic layer 5 at the second end in second directionY of bacteria inhabitable portion 202 provided with a second end 206 bof pipe 206, so that closed space 201 can be provided at the first endof bacteria inhabitable portion 202 by using the pillar members as theclosed space forming means. Second open portion 206 ba is positionedapart from bacteria inhabitable portion 202 by first distance L1 whenfirst open portion 206 ab of pipe 206 is positioned to face the firstend of bacteria inhabitable portion 202. Accordingly, aerobic region 90,aerobic layer 6, facultative anaerobic layer 5, obligatory anaerobiclayer 207, and anaerobic space 213 linking with aerobic region 90 can beeasily formed with second open portion 206 ba not closed by sand 50 andthe like. A first end 206 a of pipe 206 is located in anaerobic space213 configured by closed space 201 having an anaerobic environment andsecond end 206 b of pipe 206 is located in aerobic region 90, so thatobligatory anaerobic bacteria and products therefrom can move from firstend 206 a toward second end 206 b. Water cleaning system 210 depicted inFIG. 10 can be configured easily also by including water cleaning unit200.

Third Embodiment

The third embodiment according to the present invention will now bedescribed next with reference to FIG. 11.

In a water cleaning unit 350 according to the third embodiment of thepresent invention, only a bacteria inhabitable portion 353 having arectangular parallelepiped shape configures closing means 354 by forminga closed space 352 inside bacteria inhabitable portion 353. Pipe 206 isprovided to penetrate bacteria inhabitable portion 353 with first end206 a located in closed space 352 and second end 206 b positioned apartby first distance L1 from a second surface 353 a in second direction Yof bacteria inhabitable portion 353.

In a water cleaning unit 450 also according to the third embodiment ofthe present invention, a spherical closed space 452 is formed at thecenter of a spherical bacteria inhabitable portion 451, pipe 206 extendsfrom closed space 452 through bacteria inhabitable portion 451 servingas closing means 453, and second open portion 206 ba provided at secondend (extending end) 206 b is opened at a position apart from bacteriainhabitable portion 451 by first distance L1. In a water cleaning unit500 also according to the third embodiment of the present invention, ina case where bacteria inhabitable portion 451 is defined as a firstbacteria inhabitable portion 451, a second bacteria inhabitable portion501 having a spherical shape and inhabitable by facultative anaerobicbacteria is formed on a surface of first bacteria inhabitable portion451 and a third bacteria inhabitable portion 502 having a sphericalshape and inhabitable by aerobic bacteria is formed on a surface ofsecond bacteria inhabitable portion 501. In a case of using watercleaning unit 350, 450, or the like including neither the secondbacteria inhabitable portion nor the third bacteria inhabitable portion,sand 50 and the like can be supplied after water cleaning unit 350 or450 is installed at the bottom of the sea, for example, or watercleaning unit 350 or 450 can be buried in sea sand 300 at the bottom ofthe sea.

Fourth Embodiment

The fourth embodiment according to the present invention will now bedescribed next with reference to FIG. 12.

In water cleaning system 1 depicted in FIG. 4 and water cleaning system210 depicted in FIG. 10, breeding water 9 contains organic matterderived from hydrosphere organisms that are bred in aerobic region 90.Alternatively, water containing organic matter derived from hydrosphereorganisms can be supplied from a different place. As depicted in FIG.12, retention tank 20 used for breeding hydrosphere organisms can beprovided separately and breeding water 9 in retention tank 20 can be fedinto retention tank 2.

Specifically, in a breeding system 750 according to the fourthembodiment of the present invention, a space 290 in retention tank 20and aerobic region 90 in retention tank 2 are connected to each other byfirst water conveying means 651 and second water conveying means 652.Breeding water 9 in retention tank 20 is conveyed to retention tank 2through first water conveying means 651 whereas breeding water 9 inretention tank 2 is conveyed to retention tank 20 through second waterconveying means 652. First and second water conveying means 651 and 652include pumps P1 and P2 and hoses 651 a and 652 a that are connected topumps P1 and P2 and have ends inserted to space 290 in retention tank 20and aerobic region 90 in retention tank 2, respectively. Alternatively,breeding water 9 in retention tank 2 may not be returned to retentiontank 20 but can be conveyed to a different place. Pumps P1 and P2 andhoses 651 a and 652 a can be replaced with different members insofar asbreeding water 9 can be conveyed to retention tanks 2 and 20.

The specific configurations of the portions are not to be limitedrespectively to the embodiments described above.

Examples of breeding water 9 included in water cleaning systems 1 and210 include seawater and fresh water depending on the type ofhydrosphere organisms. Furthermore, breeding water 9 can be replacedwith water of any type containing organic matter. In a case wherebreeding water 9 is preferably kept neutral or slightly acid forbreeding of freshwater fishes or the like, coral sand 70 and the like tobe used are preferably reduced in amount to decrease the amount ofcalcium carbonate eluted into breeding water 9 in comparison to a caseof keeping slightly alkaline. In the case where fresh water is used asbreeding water 9, methanogen inhabit obligatory anaerobic layer 4 andacts similarly to sulfate-reducing bacteria B.

Two anaerobic spaces 3 are provided and tube 18 is inserted to each ofanaerobic spaces 3 in the first embodiment of the present invention.Alternatively, anaerobic spaces 3 can be connected to each other by acylindrical portion or the like and tube 18 can be inserted to only oneof anaerobic spaces 3. In this configuration, sulfate-reducing bacteriaB and hydrogen sulfide in anaerobic space 3 with no tube 18 beinginserted thereto move to anaerobic space 3 provided with tube 18 by wayof the cylindrical portion or the like and further move to aerobicregion 90 or space 290 by way of anaerobic space 3.

The number of anaerobic spaces 3 provided in the first embodiment can beone, or greater than or equal to three. Similarly to the secondembodiment, nontransmissive portion 102 can be provided at the lowerportion of side surface 2 a and on bottom surface 2 b of retention tank2 in the first embodiment. This configuration can prevent application oflight to the side surface and the lower end of obligatory anaerobiclayer 4 so as to allow obligatory anaerobic bacteria to multiplyentirely in obligatory anaerobic layer 4. There is no need to providenontransmissive portion 102 in a case where retention tank 2 does notallow transmission of light therethrough.

Water cleaning units 100, 200, 350, 450, and 500 (hereinafter, referredto as “water cleaning units 100 to 500” in order to collectively mentionthese water cleaning units) or the water cleaning method described abovecan be used or performed by sinking the water cleaning units in the sea,a lake, a pond, a river, or the like or in a farm for hydrosphereorganisms included in the water cleaning units. In a typical hydrosphereorganisms farm, part of the sea is surrounded with a net and hydrosphereorganisms are bred therein in an overcrowded state. An amount ofexcrement exceeding the amount cleaned by natural cleaning capacity canbe discharged to problematically contaminate the peripheral sea area.Use of water cleaning units 100 to 500 in such a farm achieves increasein amount of organic matter such as excrement to be decomposed andreduction in toxicity of hydrogen sulfide along with the naturalcleaning capacity, to contribute to improvement in water quality andinhibit marine contamination caused by cultivation. Furthermore, thereis no need to reduce the number of cultivated hydrosphere organisms evenafter hydrosphere organisms have grown but the number of cultivablehydrosphere organisms can be increased per unit volume in comparison toa conventional case. Retention tank 2 is not limited to a water tank,but can be a fish tank, concrete formed into a box shape having an opentop, or the like. Water cleaning system 1, 210, or 750 can be used forcultivation (breeding) of hydrosphere organisms in a fish tank or thelike. Still alternatively, a hole can be dug in the ground surface toaccommodate water cleaning system 1, 210, or 750. A soil wallconfiguring the hole corresponds to retention tank 2 in this case.

The linking means (cylindrical member) in water cleaning systems 1, 210,and 750 and the cylindrical member in water cleaning units 100 to 500are not limited to tube 18 and pipe 206 insofar as anaerobic space 3 or213 (closed space 130 or 201) and aerobic region 90 can link with eachother. For example, the linking means or the cylindrical member can beporous rock or the like that can be extended and has the second openportion at a position apart by first distance L1 from obligatoryanaerobic layer 4 or 207 or first bacteria inhabitable portion 140, 202,353, or 451. The linking means can be provided as a hole penetratingbacteria inhabitable portion 140, 141, 142, 202, 208, 209, 353, 451,501, or 502 or each of layers 4 to 7. The hole can be used by itselfwithout inserting a cylindrical member thereto.

Sea sand substantially equal in amount to andosol 40 can be furtheraccumulated above aerobic layer 6. The sea sand layer and coral layer 7can inhibit sand 50 configuring aerobic layer 6 from flying upward. Inorder to breed hydrosphere organisms such as flatfishes, shrimps, andcrabs having a habit of digging sand, a net made of stainless steel andhaving meshes sized to block passage of hydrosphere organisms ispreferably located above obligatory anaerobic layer 4 or 207, e.g.between coral layer 7 and aerobic layer 6. The net can prevent oxygenfrom entering obligatory anaerobic layer 4 or 207 due to hydrosphereorganisms digging sand 50 and andosol 40 and prevent toxic hydrogensulfide and the like generated in obligatory anaerobic layer 4 or 207from flowing out to aerobic region 90 through a hole dug by hydrosphereorganisms. The net is preferably sized and shaped to cover the entiresurface of aerobic layer 6, and its material is not limited to stainlesssteel.

Water cleaning units 100 to 500 are not limited to include firstbacteria inhabitable portions 140, 202, 353, and 451, second bacteriainhabitable portions 141, 208, and 501, and third bacteria inhabitableportions 142, 209, and 502 that are all dry. These bacteria inhabitableportions can contain moisture at a degree inhabitable by the bacteria. Asufficient number of the bacteria can preliminarily inhabit each ofbacteria inhabitable portions 140, 202, 353, 451, 141, 208, 501, 142,209, and 502.

Water cleaning system 1, 210, and 750 according to the present inventiondo not necessarily eliminate provision of a device for supplementing afiltering function such as an external filtration device or processes ofreplacing water and sand. Retention tank 2 can be additionally providedwith bacteria such as aerobic bacteria.

The above embodiments define that first direction X is horizontal andsecond direction Y perpendicular thereto is vertical. Alternatively,first direction X can be vertical and second direction Y can behorizontal or in a different direction (e.g. slanted from the horizontaldirection). In water cleaning system 1, 210, or 750 according to thepresent invention, aerobic layer 6, facultative anaerobic layer 5, andobligatory anaerobic layer 4 (207) can be formed in the mentioned orderfrom below to above, or aerobic layer 6, facultative anaerobic layer 5,and obligatory anaerobic layer 4(207) can be formed laterally.Applicable to such a situation is a case where each of water cleaningunits 100 to 500 according to the present invention is installed on aninner wall surface of a cave in the sea or the like.

In each of water cleaning units 100 to 500 according to the presentinvention, at least andosol 40 is preliminarily collected and pressed.Andosol 40 can be alternatively in a separate state. For example, eachof water cleaning units 100 to 500 can include a particulate carrierthat is the material for aerobic layer 6 and facultative anaerobic layer5 and is pressed into a block shape, loose andosol 40 not pressed,hollow member 30, meshed member 32, and plate member 31 not fixed toeach other, and tube 18 or pipe 206. Particulate carrier 50 as thematerial for aerobic layer 6 and facultative anaerobic layer 5 can beloose similarly to andosol 40. A water cleaning unit can include sand50, coral sand 70, and the like that are packed not in block shapes butin loose states and are enclosed with each of water cleaning units 100to 500.

A promoter for multiplication of obligatory anaerobic bacteria,facultative anaerobic bacteria, and aerobic bacteria (e.g. the bacteriathemselves) can be supplied upon forming water cleaning system 1, 210,or 750.

The cylindrical member such as pipe 206 can be made to be extendable.Such a cylindrical member can prevent the second end of the cylindricalmember from being buried in the layer due to accumulation of sand 50 andcoral sand 70.

The remaining configurations can be modified variously within the rangenot departing from the gist of the present invention. For example, theclosing means can be any member surrounding the closed space in order tobring the water cleaning unit according to the present inventionimmersed in water into an anaerobic state, even if the member is notdisclosed in this description. Anything forming the closed space withrespect to the water cleaning unit according to the present inventioncan serve as closed space forming means. Appropriate combination of theconfigurations according to the respective embodiments is included inthe scope of the present invention.

INDUSTRIAL APPLICABILITY

The present invention described in detail above inhibits accumulation oftoxic matter derived from organic matter discharged from hydrosphereorganisms, reduces toxicity of hydrogen sulfide generated from organicmatter derived from hydrosphere organisms due to activity of bacteria byconverting into a less toxic substance, so as to be useful with none ofrequirements of a device for supplementing a filtering function andprocesses of replacing water and sand semipermanently or for a longperiod of time.

REFERENCE SIGNS LIST

-   1, 210, 750: Water cleaning system; 2: Retention tank; 3, 213:    Anaerobic space; 4, 207: Obligatory anaerobic layer; 5: Facultative    anaerobic layer; 6: Aerobic layer; 18 ab, 206 ab: First open    portion; 18 ba, 206 ba: Second open portion; 9: Water (Breeding    water); 18, 206: Linking means, Cylindrical member (Tube, Pipe); 30:    Hollow member; 30 a: Opening of hollow member; 32: Meshed member;    40: Soil material (Andosol); 50: Particulate carrier (Sand); 70:    Coral sand; 90: Aerobic region; 100, 200, 350, 450, 500: Water    cleaning unit; 102: Nontransmissive portion; 130, 201, 352, 452:    Closed space; 132: Closing means; 140, 202, 353, 451: First bacteria    inhabitable portion; 141, 208, 501: Second bacteria inhabitable    portion; 142, 209, 502: Third bacteria inhabitable portion; 202 a:    Penetrating portion (Cylindrical member insertion hole); 551:    Support leg; 552: Installation surface; G: Gap; L1; Predetermined    distance (First distance)

1. A water cleaning system comprising: an aerobic region including watercontaining organic matter and oxygen; an aerobic layer linking with theaerobic region and inhabited by aerobic bacteria; a facultativeanaerobic layer provided adjacent to the aerobic layer and inhabited byfacultative anaerobic bacteria; an obligatory anaerobic layer providedadjacent to the facultative anaerobic layer, inhabited by obligatoryanaerobic bacteria, and made of a soil material; an anaerobic spacehaving an anaerobic environment, allowing the obligatory anaerobicbacteria inhabiting said obligatory anaerobic layer and productstherefrom to flow therein; and linking means linking the anaerobic spaceand said aerobic region.
 2. The water cleaning system according to claim1, wherein an opening at a top of a hollow member is closed by a meshedmember having water permeability and blocking passage of said soilmaterial, said soil material surrounds the hollow member and the meshedmember to form said anaerobic space in said hollow member.
 3. The watercleaning system according to claim 2, wherein said soil material isandosol.
 4. The water cleaning system according to claim 3, wherein saidaerobic layer is provided, on a surface thereof, with a layer made ofcoral sand.
 5. The water cleaning system according to claim 1, whereinsaid retention tank includes a nontransmissive portion blockingtransmission of light from a lower portion in a side surface and from abottom surface, a meshed member having water permeability and blockingpassage of said soil material is entirely provided at a lower portion inthe retention tank so as to be apart from an inner bottom surface ofsaid retention tank, the meshed member has an upper surface covered withsaid soil material and said anaerobic space is formed between the meshedmember and said inner bottom surface.
 6. A water cleaning methodcomprising: installing, in water, a first bacteria inhabitable portionmade of a soil material that is inhabitable by obligatory anaerobicbacteria and preliminarily pressed into a massive shape, forming, inwater, a second bacteria inhabitable portion that is adjacent to thefirst bacteria inhabitable portion, has a particulate carrier, and isinhabitable by facultative anaerobic bacteria, a third bacteriainhabitable portion that is adjacent to the second bacteria inhabitableportion, has a particulate carrier, and is inhabitable by aerobicbacteria, and an anaerobic space that has an anaerobic environment andlinks with said first bacteria inhabitable portion, locating, at aposition linking with said third bacteria inhabitable portion, anaerobic region including organic matter and oxygen, and linking theaerobic region and said anaerobic space, and forming an obligatoryanaerobic layer by multiplying obligatory anaerobic bacteria in saidfirst bacteria inhabitable portion, forming a facultative anaerobiclayer by multiplying facultative anaerobic bacteria in said secondbacteria inhabitable portion, forming an aerobic layer by multiplyingaerobic bacteria in said third bacteria inhabitable portion, causingthese bacteria to decompose the organic matter in said aerobic region,and moving the obligatory anaerobic bacteria flowing out of saidobligatory anaerobic layer and products therefrom from said anaerobicspace to said aerobic region.
 7. A startup method for the water cleaningsystem according to claim 1, using a cylindrical member as said linkingmeans, the method comprising: applying light to said aerobic layer in astate where said aerobic region includes organic matter andsimultaneously supplying gas from gas supply means into said cylindricalmember to generate a stream from said anaerobic space toward saidaerobic region in said cylindrical member, and keeping the state for apredetermined period of time.
 8. A water cleaning unit used forconstructing the water cleaning system according to claim 1, the watercleaning unit comprising: a bacteria inhabitable portion in a massiveshape, made of a soil material and inhabitable by obligatory anaerobicbacteria; and a cylindrical member that has a first open portion and asecond open portion, has a length to extend from a first end to a secondend of said bacteria inhabitable portion, wherein said second openportion is positioned apart from said bacteria inhabitable portion by apredetermined distance at the second end of said bacteria inhabitableportion when said first open portion is positioned to face the first endof said bacteria inhabitable portion.
 9. The water cleaning unitaccording to claim 8, further comprising: a closed space surrounded withclosing means that is at least partially formed by said bacteriainhabitable portion; wherein said cylindrical member has a length toextend from said closed space through said closing means, and saidsecond open portion is positioned apart from said bacteria inhabitableportion by a predetermined distance when said first open portion ispositioned to face said closed space.
 10. The water cleaning unitaccording to claim 9, wherein at least a surface, not provided with saidcylindrical member projecting therefrom, of said bacteria inhabitableportion is covered with a surrounding member blocking passage of saidsoil material.
 11. The water cleaning unit according to claim 10,wherein said surrounding member has a light shielding property.
 12. Thewater cleaning unit according to claim 11, wherein said bacteriainhabitable portion and said closed space are provided therebetween witha meshed member having water permeability and blocking passage of saidsoil material.
 13. The water cleaning unit according to claim 12,further comprising a particulate carrier inhabitable by aerobic bacteriaand facultative anaerobic bacteria to form, when said bacteriainhabitable portion inhabitable by obligatory anaerobic bacteria isdefined as a first bacteria inhabitable portion, a second bacteriainhabitable portion that is adjacent to the first bacteria inhabitableportion and is inhabitable by facultative anaerobic bacteria and a thirdbacteria inhabitable portion that is adjacent to the second bacteriainhabitable portion and is inhabitable by aerobic bacteria.
 14. Thewater cleaning unit according to claim 13, wherein said bacteriainhabitable portion is dry.
 15. The water cleaning unit according toclaim 14, further comprising a support leg for securing a predeterminedgap from an installation surface.